Michael Schumacher completed Mercedes' most promising day of testing this season with the fastest time and a very healthy 112 laps of the Jerez circuit.

Questions were starting to be asked of the new W02, after problems with its hydraulics restricted running in the opening test at Valencia and its lap times were a long way off the front runners. On Thursday at Jerez Mercedes announced it had made a break through with the reliability of the car and on Friday Schumacher rocketed to the top of the timing screens.

Although the timings should still be treated as little more than a very rough guide, the performance makes Mercedes the fourth different team to have finished a test day on top, joining Red Bull, Ferrari and Renault.

Of those four, Ferrari has been the most consistent and again Felipe Massa was at the sharp end, just 0.061 off Schumacher. He completed a whopping 116 laps to add to his 101 on Thursday, meaning he has completed over three race distances in two days. Once again the F150th Italia didn't appear to skip a beat and the only setback came when red flags stopped the session.

There were two in the morning for what looked like mechanical issues on the Renault and Toro Rosso and two further stoppages in the afternoon for accidents. Rookies Sergio Perez and Pastor Maldonado both blotted their copybooks with sizable accidents that put an end to their days. Perez ripped the front wing of the Sauber clean off and made a mess of the front left suspension. Maldonado also wiped the front wing of his Williams off and caused damage to the rear left suspension as the car ended up with its back end in the tyre barriers. Perez still ended the session in seventh after putting in some quick laps early on, while Maldonado was ranked ninth with just 37 laps against his name.

McLaren continued to ease its way into testing, with Jenson Button putting 61 laps on the new MP4-26 and logging the third fastest time, 0.6 seconds shy of Schumacher. The team insists it has not yet run the new car at anything approaching full speed and is instead testing the reliability of its systems and solving teething problems.

Meanwhile, Jaime Alguersuari put in a very solid lap in the Toro Rosso for fourth place in the standings, but like all the drivers is not getting distracted by the timing screens. "In performance terms, it is still a bit too early to start drawing conclusions, especially as the lap times here vary a lot from the morning to the afternoon," he said. "But I am reasonably confident that this side of the car's progress is on the right track."

Virgin was another team that made an improvement, with Timo Glock logging the eighth fastest time, 1.8 seconds off Schumacher's pace. The same could not be said of rivals Lotus, who spent most of the afternoon in the garage fixing a mechanical problem. New parts will arrive over night to address the issue.